The UK National External Quality Assessment Scheme in Blood Group Serology. Compatibility testing 1979–1980

Seven proficiency tests in compatibility testing were issued in 1979 to 1980. In each exercise participants were required to test five sera, most of which contained alloantibodies, against three samples of red cells by three designated techniques, namely agglutination in saline at room temperature, agglutination in albumin at 37°C and the antiglobulin test at 37°C. Comparability was achieved by scoring of results. Incompatibilities were missed by 3.5 to 22% of participants in five exercises in which undiluted antibodies were issued. There was no significant improvement in performance over two years. Antibodies which were issued diluted, but detectable by antiglobulin test, were missed with high frequency.     

The UK National External Quality Assessment Scheme in Blood Group Serology. Compatibility testing 1979–1980: trends and performance in relation to practice in antiglobulin testing

Summary Surveys of antiglobulin test procedures and reagents were undertaken in 1979-1980 as part of a national external quality assessment scheme in compatibility testing. An extraordinary lack of standardization was revealed. In addition, practices underwent considerable changes over this period. The use of tube and of low ionic strength solution (LISS) techniques increased whilst the use of tile and of albumin-antiglobulin techniques declined. Performance in compatibility test exercises was significantly better with tube techniques than with tile techniques in 9/22 incompatibilities. Performance with LISS techniques was occasionally significantly better than with normal ionic strength techniques. Performance with albumin-antiglobulin techniques was occasionally significantly worse than in the absence of albumin. To varying extents significant relationships were found between performance and cell concentration, serum/cell concentration ratio, antiglobulin reagent and method of reading the results.     

The UK National External Quality Assessment Scheme in Blood Group Serology. Compatibility testing 1979–1980: trends and performance in relation to practice in antiglobulin testing

Summary Surveys of antiglobulin test procedures and reagents were undertaken in 1979–1980 as part of a national external quality assessment scheme in compatibility testing. An extraordinary lack of standardization was revealed. In addition, practices underwent considerable changes over this period. The use of tube and of low ionic strength solution (LISS) techniques increased whilst the use of tile and of albumin-antiglobulin techniques declined. Performance in compatibility test exercises was significantly better with tube techniques than with tile techniques in 9/22 incompatibilities. Performance with LISS techniques was occasionally significantly better than with normal ionic strength techniques. Performance with albumin-antiglobulin techniques was occasionally significantly worse than in the absence of albumin. To varying extents significant relationships were found between performance and cell concentration, serum/cell concentration ratio, antiglobulin reagent and method of reading the results.     

The UK National External Quality Assessment Scheme in Blood Group Serology. Compatibility testing 1983–1984: the influence of variables in test procedures on detection of incomplete antibodies

Summary Error rates in exercises in compatibility testing varied between 3% and 36% over the six years 1979–1984. Evolution of serological procedures was continuous through this period but without clear evidence of improvement in performance of antibody detection although performance in the UK appears to be comparable with that elsewhere. Relationships have been established between a number of variables of reagents and techniques, and their performance. The influence of some variables is reasonably clear but there appear to be interactions between certain variables in their effects on performance, and interpretation is less straightforward. A test for agglutination of enzyme treated cells together with an antiglobulin test appears to be the most reliable combination for detection of incomplete antibodies in compatibility testing although one stage enzyme techniques are an inevitable compromise between reliability and convenience. Compatibility testing should not be considered in isolation from antibody screening in determining the optimum combination of tests for pre-transfusion antibody detection.     

The UK National External Quality Assessment Scheme in Blood Group Serology. ABO and D grouping and antibody screening 1982-1983

In seven surveys of blood grouping the overall rates of major error were 0.12% and 0.37% for uncomplicated ABO and D grouping respectively. Of 17 errors of ABO grouping, 13 were errors of transposition or interpretation and four were apparently technical. Of 52 errors of D grouping, 20 appeared to be errors of transposition or interpretation and 32 were apparently technical. Of the 32 technical errors of D grouping, 31 were D-negative grouped as Du (29) or D-positive (2) and most of these errors were due to misgrouping in the antiglobulin test. Causes of error in D grouping by antiglobulin test include anti-Bg and other contaminating immune antibodies, residual unabsorbed anti-A and the inherently high rate of false positive results obtained in the antiglobulin test. In view of the lack of benefit of Du testing to blood recipients or to pregnant women and of the possible adverse consequences of misgrouping D-negative patients as Du or D-positive, it is recommended that Du testing be abandoned in these groups of patients. The surveys of antibody screening demonstrated lack of standardisation and error rates similar to those previously reported in the UK for compatibility testing.     

The UK National External Quality Assessment Scheme in Blood Group Serology. ABO and D grouping,antibody screening,direct antiglobulin test and antibody identification 1984–1985

Summary In seven exercises of blood grouping the overall rates of major error were 0.19% and 0.25% in ABO and D grouping respectively. In ABO grouping this represents an increase in error rate over that observed in 1982–1983 but the increase was due to an unusually high error rate with one particular group A₂B cell. An improvement in performance was observed in simple D grouping and was largely due to a lower incidence of false positive grouping of D-negative cells in the antiglobulin test. An improvement in performance observed in D grouping IgG-coated D-negative cells appeared to be due to a better understanding of the problem rather than to any change in serological practice. Error rates in antibody screening were somewhat lower than in 1982–1983 but this may or may not represent an improvement in performance as the test materials were not the same in the two periods. The direct antiglobulin test with IgG-coated cells was reliably performed with polyspccific and with anti-IgG reagents but an excess of false positive results was obtained with anti-C3d. Error rates in antibody identification varied from 0.6% for anti-D to 74% for anti-c + E.     

The UK National External Quality Assessment Scheme in Blood Group Serology. Compatibility testing 1983-1984: the influence of variables in test procedures on detection of incomplete antibodies

Error rates in exercises in compatibility testing varied between 3% and 36% over the six years 1979-1984. Evolution of serological procedures was continuous through this period but without clear evidence of improvement in performance of antibody detection although performance in the UK appears to be comparable with that elsewhere. Relationships have been established between a number of variables of reagents and techniques, and their performance. The influence of some variables is reasonably clear but there appear to be interactions between certain variables in their effects on performance, and interpretation is less straightforward. A test for agglutination of enzyme treated cells together with an antiglobulin test appears to be the most reliable combination for detection of incomplete antibodies in compatibility testing although one stage enzyme techniques are an inevitable compromise between reliability and convenience. Compatibility testing should not be considered in isolation from antibody screening in determining the optimum combination of tests for pretransfusion antibody detection.     

The UK National External Quality Assessment Scheme in Blood Group Serology. ABO and D grouping, antibody screening, direct antiglobulin test and antibody identification 1984-1985

In seven exercises of blood grouping the overall rates of major error were 0.19% and 0.25% in ABO and D grouping respectively. In ABO grouping this represents an increase in error rate over that observed in 1982-1983 but the increase was due to an unusually high error rate with one particular group A2B cell. An improvement in performance was observed in simple D grouping and was largely due to a lower incidence of false positive grouping of D-negative cells in the antiglobulin test. An improvement in performance observed in D grouping IgG-coated D-negative cells appeared to be due to a better understanding of the problem rather than to any change in serological practice. Error rates in antibody screening were somewhat lower than in 1982-1983 but this may or may not represent an improvement in performance as the test materials were not the same in the two periods. The direct antiglobulin test with IgG-coated cells was reliably performed with polyspecific and with anti-IgG reagents but an excess of false positive results was obtained with anti-C3d. Error rates in antibody identification varied from 0.6% for anti-D to 74% for anti-c + E.     

Multilaboratory testing in thrombophilia through the United Kingdom National External Quality Assessment Scheme (Blood Coagulation) Quality Assurance Program

We describe here results from the United Kingdom National External Quality Assessment Scheme (UK NEQAS) Thrombophilia Screening Program, in which an average of 21% of 280 centers reported an incorrect diagnosis for a series of plasma samples. Three case studies are described, showing causes of error in individual laboratories, related to the source of reference plasma or reagents. Methodological bias is also described. For protein C (PC) assays 18% of centers reported PC deficiency in a patient homozygous for factor V Leiden. Studies in the NEQAS laboratory confirmed the effect of activated protein C resistance (APCR) on clot-based PC activity assays. Differences in results obtained for PS-deficient subjects with different protein S (PS) activity kits are reported; several subjects would be misdiagnosed as normal with one kit if the manufacturer's reported reference range was adopted instead of a locally determined reference range. Antithrombin (AT) assays were shown to vary in their sensitivity to different molecular defects in the antithrombin gene; 77% of centers employing human thrombin-based activity assays reported a normal AT level in a patient with antithrombin Cambridge II. Sensitivity of the APC resistance test in the absence of factor V-deficient plasma was shown to be improved through normalization of results, and errors in the genetic diagnosis of factor V Leiden and the P20210A prothrombin gene mutation are described. Errors in the diagnosis of thrombophilic defects can therefore be identified through participation in EQA programs, and following dissemination of information, improvements in diagnosis can be demonstrated.     

External Quality Assessment of Blood Glucose Monitors: Problems and Practical Solutions in the External Quality Control of Point of Care Devices with Respect to the Measurement of Blood Glucose

Point of care testing (POCT) is evolving at an ever increasing rate. This article deals mainly with the aspect of POCT for blood glucose and the problems of external quality assessment (EQA) of point of care devices (POCD). At the present time it is only possible to control precision with EQA, independent of the matrix of the test materials (synthetic polymer-base, plasma/serum, or processed whole blood). The German Federal Medical Council guidelines for laboratory performance allow an interlaboratory imprecision of ±16%. The majority of POCD fulfill these requirements. The long-term stability of results—tested by repeated distribution of the same materials over a 12-month period—is excellent, and the performance of POCD under routine condtions is usually excellent in terms of result-comparability. The problems of accuracy in terms of control materials have still to be mastered.     

Proficiency testing in immunohaematology in Ontario,Canada, 1977–1979

Summary. An analysis of the results of a compulsory proficiency testing programme in immunohaematology is presented. Error rates have been calculated for the determination of ABO and Rh(D) groups, the direct antiglobulin test and antibody detection according to defined criteria. The introduction of proficiency testing has been associated with alterations in error rates for some determinations. An educational programme introduced for laboratories with poor performance has proved effective in improving their results in the proficiency testing programme.     

Variants of RhD – current testing and clinical consequences

Anti‐D (‐RH1) of the Rh blood group system is clinically important as it causes haemolytic transfusion reactions and haemolytic disease of the fetus and newborn. Although most people are either D+ or D−, there is a plethora of D variants, often categorized as either weak D or partial D. These two types are inadequately defined and the dichotomy is potentially misleading. DVI is the D variant most commonly associated with anti‐D production and UK guidelines recommend that patients are tested with anti‐D reagents that do not react with DVI. Weak D types 1, 2, and 3 are seldom, if ever, associated with alloanti‐D production, so a policy recommendation would be to treat patients with those D variants as D+, to preserve D− stocks, whereas patients with all other D variants would be treated as D−. All donors with D variant red cells, including DVI, should be treated as D+.     

Variability in factor V:C assays in UK National External Quality Assessment Scheme surveys: there is a need for an international standard.

Severe familial factor V:C deficiency is a rare, recessively inherited coagulation disorder but there is little information in respect of the accuracy and reliability of factor V:C assays that are required for diagnosis and treatment monitoring. We present here the results of three External Quality Assessment exercises in respect of factor V:C assays undertaken by 192--225 participating laboratories performed over a 2-year period. Consistent significant differences were observed between results obtained using different reference plasmas and different thromboplastins. The relationship between results obtained with different reference plasmas was not constant and varied between the surveys. In-house studies confirmed the observation derived from the External Quality Assessment surveys that the choice of commercial reference plasma significantly affects the results of factor V:C assays. These results clearly indicate the necessity for an international standard for factor V:C.     

Reduction of the risk of transfusion‐transmitted viral infection by nucleic acid amplification testing in the Western Cape of South Africa: a 5‐year review

Background and Objectives In October 2005, individual donation nucleic acid amplification testing (ID‐NAT) for HIV, HBV and HCV was introduced in the Western Cape Province of South Africa. After 5 years, the impact on HIV, HBV and HCV transmission risk was assessed. Materials and Methods A total of 649 745 donations were tested by ID‐NAT using the Ultrio assay on the Tigris instrument (Novartis Diagnostics) and for anti‐HIV, HBsAg and anti‐HCV (Abbott Prism). Initial reactive samples were repeated in duplicate. Discrepant repeat reactive samples were subjected to confirmatory assays. ID‐NAT nonrepeat reactive donations were further screened for occult HBV infection (OBI) by anti‐HBc assay. Results ID‐NAT yielded 6 HIV‐RNA‐positive donations in the anti‐HIV‐negative window period (WP) but only 2 were p24 Ag nonreactive (1:325 000). Mathematical modelling estimated a similar HIV transmission risk for lapsed and repeat donations, in the order of 3 per million. The WP risk for HBV was 13 per million. Eight acute (1:81 000) and 13 chronic OBI yield cases (1:50 000) were interdicted. There were significantly more anti‐HBc‐positive donors in the Ultrio initial reactive/nonrepeat reactive group (12%) than in an Ultrio nonreactive control group (6%). Conclusion ID‐NAT in the Western Cape Province of South Africa has contributed significantly to enhancing blood safety, particularly for HBV transmission risk and to a lesser extent for HIV. Anti‐HBc testing of NAT nonrepeat reactive donations seems useful in identifying a subgroup of donors with OBI who may be at risk of transmitting HBV.     

Hepatitis E virus infection in Ghanaian blood donors – the importance of immunoassay selection and confirmation

Background and Objectives Hepatitis E virus (HEV) infection is emerging as a potential new threat to blood safety after several cases of transfusion–transmission were reported from non‐epidemic countries. On the basis of seroprevalence data, HEV is endemic in Ghana where poor sanitary conditions and regular flooding are prevalent. However, no data are available for HEV prevalence in blood donors. Materials and Methods Plasma samples from 239 Ghanaian blood donors were tested for anti‐HEV IgG and IgM by ELISA (two and three assays, respectively) and Western blot (recomLine) and for HEV‐RNA by RT‐qPCR. Results All donors were RNA negative. Results from the different serological assays were discrepant: reactivity in two of the three IgM assays was correlated with elevated IgM levels, but the discrepancies between IgG assays were unrelated to the donors’ IgG levels and more likely related to assay sensitivity. Fourteen samples (5·9%) were anti‐HEV IgM reactive and 11 samples (4·6%) anti‐HEV IgG reactive in at least two serological assays from different manufacturers. Conclusions (a) In the absence of accepted confirmatory assays, it is crucial to confirm anti‐HEV reactive samples with an alternative assay, especially when the population tested carries high levels of immunoglobulin M. (b) Although asymptomatic HEV infections are common in Ghanaian blood donors, currently, it does not seem to be a major risk to blood safety.     

A, B and H Blood Group Specificities in Glycoprotein and Glycolipid Fractions of Human Erythrocyte Membrane. Absence of Blood Group Active Glycoproteins in the Membranes of Non-Secretors

Abstract. Blood group A-, B- and H-activities were studied in glycolipid and glycoprotein fractions of human erythrocyte stroma derived from secretors and non-seeretors. A- and B- but not H-specificities were detected in stroma glycolipids irrespective of the secretor status of blood donors. On the other hand A-, B- and H-specificities in glycoprotein fractions of stroma were present only in erythrocytes of secretors. Glycoprotein extracts of stroma of non-secretors did not contain A- and B-specificity.